D 2.x invariant question
Charles D Hixson
charleshixsn at earthlink.net
Wed Oct 31 18:53:22 PDT 2007
Jarrett Billingsley wrote:
> "Charles D Hixson" <charleshixsn at earthlink.net> wrote in message
> news:fgao71$21fp$1 at digitalmars.com...
>> Would the following function:
>> invariant Body opIndex (Key k)
>> { if (k in _cache)
>> { ....
>> return _cache[k].bdy;
>> }
>> return null;
>> }
>>
>> return values that were invariant, or would that type have to be declared
>> at the declaration of the type "Body"?
>
> I think this makes the method opIndex invariant, which means this function
> can only access invariant members, or something. If you want an
> invariant(Body), use... invariant(Body) as the return type.
>
> Aside: performance increase, you can avoid the double lookup:
>
> if(auto val = k in cache)
> {
> ..use val here..
> return val.bdy;
> }
>
> 'in' returns a pointer to the value, and you can declare and assign a
> variable in the condition of an 'if' statement.
>
>
Thanks.
(I *kenw* that about "in", but I keep forgetting.)
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